var arr = new Array(); 
arr = [{
    "subject.1": {
        "name.11": "机械制图hghgjh",
        "tip.12": {
            "ls.121":"1111111111",
            "ds.122":"2222222222"
        },
        "chapter.13": {
            "name.131": "第一章 制图的基本知识和技能",
            "section.132":{
                "tip1.1321":"test1",
                "tip2.1322":"test2"
            },
            "section.133": "制图国家标准的基本规定"
        }, 
        "chapter.14": {
            "name.141": "第二章 ",
            "tip1.142": "qqqqqqq",
            "tip1.143": "钱22222"
        }
        
    },
    "subject.2": {
        "name.21": "基础",
        "tip.22": "mb",
        "chapter.23": {
            "name.231": "绪论",
            "tip2.232": "机器的组成",
            "tip2.233": "机构的结构"
        },
        "chapter.24": {
            "name.241": "第一章 力系与平衡",
            "tip.242": "力的概念",
            "tip.243": "力的基本性质"
        }
    }
}]

console.log(arr[1])